1. Field of the Invention
The invention relates generally to the field of molding of plastic articles and, more particularly, to a method and apparatus for trimming molded plastic articles, especially with a heat treatment means.
2. Description of the Related Art
Procedures for blow molding double wall plastic articles typically involve the formation of flash or excess material around the perimeter of the part being formed. This flash is pressed thin, or "pinched off" by means of metal to metal contact areas of the opposing mold halves, at the mold parting line and adjacent to the mold cavity or cavities. This pinchoff area is typically relatively wide, on the order of 0.025 to 0.050 inches. When the flash is torn or cut from the molded part, a significant amount of the pinched flash remains attached to said part and must be subsequently removed by mechanical trimming.
In response to the pinchoff problem, a mold construction was developed which is known as "zero land" construction whereby the amount of pinch flash produced is greatly reduced. However, when the flash is removed from the part, the remaining parting line edge is sharp. This sharp edge is unacceptable in some instances. For example, plastic cases manufactured to hold children's toys cannot have sharp edges due to the risk of injury to children.
In both of the above processes, pinchoff and sharp edges have traditionally been removed by hand with a knife. This hand trimming causes several problems, such as the direct increase in labor cost, inconsistent trimming quality and the possibility of repetitive motion syndrome in the wrists of the hand trimmers.
Another approach has been to heat trim the edges of "zero land" molded articles with a hand held propane torch. This method produces acceptably rounded edges of the articles but still involved the above-described problems associated with hand trimming.
It is therefore desirable to trim blow molded plastic articles in a procedure which does not involve substantial additional labor costs, which produces consistent quality trimming, and which does not pose the risk of injury to operators.
It is, therefore, the principal object of the present invention to provide an apparatus for trimming blow molded plastic articles which does not involve a "by hand" procedure.
It is a further object of the present invention to provide an apparatus for trimming such plastic articles which produces consistent quality trimming of sharp edges of plastic molded articles, especially with a heat treatment means.
It a still further object of the present invention to provide an apparatus and method for trimming molded plastic articles which does not involve repetitive hand motions of operators and which, therefore, does not pose the risk of repetitive motion syndrome.
Other objects and advantages will become apparent to those skilled in the art upon a consideration of the following disclosure of the invention.